1. Field
The present application relates to an electromagnetic damper, which causes oscillation damping force using a motor driven with energy (an electrical power) from a power source.
Development of electromagnetic dampers has been promoted in recent years so as to increase ride comfort or operational stability of automobiles. Japanese Unexamined Patent Application Publication No. 2006-057668 discloses a shock absorber D including a movement conversion mechanism T, which converts a linear relative movement of a vehicle body B and an axle into rotary movement, and a motor M to which the rotary motion resulting from the conversion of the movement conversion mechanism T is transmitted (see Abstract).
Japanese Unexamined Patent Application Publication No. 2006-057668 mentions a case in which expansion and contraction of the shock absorber D are controlled by actively supplying current from an external power source to winding 7 of the motor M and adjusting rotational torque (see [0045]).
Typically, when a vehicle is stopped, the vehicle height or vehicle body position changes as the weight of a load changes due to getting on or off of an occupant, loading or unloading the vehicle, or the like. If even while the vehicle is stopped, power continues to be supplied to a motor from a power source, such as a battery, the accumulated power is consumed quickly. If while the vehicle is stopped, the power supply from the power source to the motor is stopped, it is difficult to damp the oscillation of the vehicle body using the electromagnetic damper, which depends on the change in the above-described vehicle height or vehicle body position.
In terms of the power consumption caused by the electromagnetic damper, the above-described disadvantages may occur not only at the times when the vehicle is stopped.